Chengdu Mytech Biotech Co.,Ltd. Product R&D Department
What is heat stress of layer?
Heat stress of layer is a series of physiological reactions and symptoms caused by the high temperature, which exceeds the heat tolerance range of chickens, resulting in the inability to maintain normal body temperature. The optimum temperature for the growth of layer is 18℃-25℃, and when it is higher than 28.5℃, the body temperature of the layer increases, the feed intake decreases, and the consumption of water increases. If the temperature exceeds 37 ℃ for a long time, the chickens will die.
Production harm and economic loss caused by heat stress of layer
❤ Decrease in feed intake: It was found that at 21°C-30°C, feed intake decreased by 1.5% for every 1°C increase, while at 32°C-38°C, feed intake decreased by 4.6% for every 1°C increase
❤ Increased consumption of drinking water will lead to watery feces: watery feces will result in unfavorable transportation of feces and increased dosage of auxiliary materials
❤ Egg production rate and egg weight decrease rapidly: When the ambient temperature is higher than 30℃ and the humidity exceeds 65%, the egg production rate and egg weight decrease obviously.
❤ Eggshell quality decreased: mainly the dirty eggs and broken eggs increase by 1-2%
❤ Economic loss: Taking 10,000 layer as an example, if the number of defective eggs increases by 1-2%, the comprehensive economic loss will be nearly 10,000-20,000 yuan per year
Physiological changes caused by heat stress of layer
(1) Acid-base imbalance and calcium metabolism imbalance caused by gasping
Layer does not have sweat glands and dissipate heat mainly through mouth-open breathing and excretion. Gasping accelerates the massive excretion of CO2 from the lungs, causing a decrease in the concentration of bicarbonate (H2CO3) and hydrogen ions (H +) in the blood, increasing the blood pH, causing respiratory alkalosis. In order to maintain normal blood pH, poultry will begin to excrete more HCO3- and retain H + from the kidneys. When respiratory alkalosis occurs, calcium carbonate used to form eggshells is reduced; Calcium carbonate deposited in the bones is destroyed to replace the loss of carbonic acid in the blood, leading to bone problems; More HCO 3 - and calcium and potassium plasma are excreted through the kidneys, and the electrolyte balance is imbalanced; The secretion of calcium carbonate by the shell glands is reduced, resulting in eggshell defects.
(2) The intestinal tract digests and absorbs less nutrients
The heat balance of the body is broken, the excitability of the feeding center is reduced, and the reduction of feed intake will reduce the nutritional intake level of layer. At the same time, the increase of water intake leads to the filling of the digestive tract, compresses the mechanoreceptors of the digestive tract, and negatively feeds back to the eating center, further reducing the feed intake of layer.
(3) Endocrine disorders, decreased ovarian activity and function
Under heat stress, the neuroendocrine system of layer will change, resulting in a decrease in the secretion of follicle stimulating hormone and luteinizing hormone, and an increase in the levels of adrenocorticotropic hormone and adrenocorticosterone in the blood, resulting in a decrease in ovarian activity and function.
Nutritional regulation measures to heat stress of layer
(1)Regulating electrolyte balance
Heat stress causes respiratory alkalosis in layer, resulting in acid-base ion imbalance in the body. In production, 1% calcium bicarbonate (CaHCO3), 0.5% sodium bicarbonate (NaHCO3), 1% ammonium chloride (NH4Cl), 0.6% potassium chloride (KCl), etc. are commonly used to regulate the ion balance in the body, so that its electrolyte balance value (DEB) reaches 250mEq/kg.
(2) Ensure adequate nutrient supply
In order to ensure adequate nutrition intake of layer, the levels of energy, amino acids, vitamins and minerals in the diet should be improved. The specific measures are as follows:
❤ Energy: Carbohydrates produce more heat than fat in the process of digestion and utilization. Replacing part of corn with soybean oil is conducive to lowering body temperature, increasing feed palatability and prolonging residence time;
❤ Protein and amino acids: the metabolism of protein of layer will produce heat and more nitrogen emissions, so it is recommended to appropriately reduce protein levels in diets, increase lysine and methionine levels, and balance amino acid levels.
❤ Vitamins: VA, VC, and VE have certain antioxidant capacity, which can reduce the negative effects of heat stress on layer. The recommended vitamin dosage (9000IU/kgVA, 200mg/kgVC, 150mg/kgVE);
❤ Mineral elements: Chromium (Cr) can regulate hormone secretion of layer, selenium (Se) can regulate immune and antioxidant capacity of layer, and appropriate supplementation of trace elements Cr and Se, as well as macro elements calcium (Ca) and phosphorus (P) is beneficial to improve eggshell quality. It is recommended that the dosage of Cr is 1-2mg/kg, and that of Se is 0.5-0.8 mg/kg.
(3) Improve the digestion and absorption capacity of nutrients
Improve the nutrient conversion efficiency of layer, such as adding functional components (such as enzymes, small molecule active peptides, etc.)
Application case of nutritional regulation scheme for heat stress of layer
(1) Composition
❤ Nutritional regimen: Add 3kg/T small molecule active peptide to reduce CP by 0.3% and 30kcal/kgME
❤ Cost change: reduced by 17 yuan/ton
(2) Proofs
❤ Small molecule active peptides are rich in active peptides that promote intestinal growth and development and structural integrity, and rich in extremely strong antioxidant peptides. They play two functions in layer:
❤ On the one hand, it can improve the digestion and utilization rate of nutrients and enhance the digestion and absorption capacity (intestinal health)
❤ On the other hand, it can reduce the oxidative damage of the body (anti-stress ability)
(3) Evaluation:
❤ Testing subject: Roman gray, after 610 days of age (after forced moult)
❤ Testing time: July-October (Temperature: above 30℃ in pens, about 40℃ outdoor)
❤ Testing period: pre-feeding period 2 weeks + formal period 12 weeks
❤ Test grouping: One row in the same building was selected as the control group and the small molecule active peptide group, with about 1000 chickens in each row (about 5 chickens in each cage), totaling about 2000 chickens.
❤ Experimental diet: The same original formula diet was fed in the pre-trial period, and different formula diets were fed in the formal trial period: the control group use the original formula diet, and the experimental group use the small molecule active peptide diet.
After 12 weeks of official application, let's see the result?
1 Improve egg laying performance
(1) Increase the egg production rate by 1.81% and reduce the feed-to-egg ratio by 0.05
(2) Reduce the rate of defective eggs by 0.82% (mainly reducing dirty eggs)
2 Improve egg quality
(1) Reduce white eggs by 12-15%
(2) Egg quality (increase eggshell strength by 13%, increase eggshell thickness by 5%)
Note: 120 eggs were selected per group for eggshell color grading.
(3) Improve intestinal and liver health and reduce the proportion of abdominal fat
After 12 weeks of use, the small intestine is longer, heavier, and more tougher, the liver is healthier, and the abdominal fat is lower
(4) Improve fecal quality
When adding small molecule active peptide, the supernatant of feces was clearer after 7 days of storage, which reflected that the intestinal digestion and absorption of layer were better
Application value
Under heat stress environment in summer, the addition of small molecule active peptide can alleviate the decrease rate of egg production and reduce the number of defective eggs
Application effect:
❤ Slowing down the decrease rate of egg production rate by 1.81% and reducing the feed-to-egg ratio by 0.05;
❤ Reduce the rate of defective eggs by 0.82%, among which dirty eggs and broken eggs are the main ones: ① Improve the quality of feces and reduce fecal eggs; ② Increase the strength of eggshell by 13%, increase the thickness of eggshell by 5%, and reduce the pollution of eggs with egg white liquid.
Path of action:
Small molecule peptides improve intestinal health, liver and intestinal health of layer under heat stress conditions
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